For the Vanilla Custard, I followed a recipe provided by Smitten Kitchen, who shared this Pastry Cream recipe by Dorie Greenspan. For the tart crust, see below:
Almond Tart Crust, adapted from Quick Vegetarian Pleasures, by Jeanne Lemlin
5 tablespoons unsalted butter, softened
1 large egg yolk
1/2 teaspoon vanilla extract
3 tablespoons maple sugar (or other sugar)
2/3 cup almonds, finely ground after measuring
1/2 cup whole wheat flour
1/2 cup other flour (all purpose, oat flour, barley flour or other)
1. Grease a 9 or 10 inch tart pan with removable bottom or a pie pan.
2. In a large bowl, beat the egg yolk with the butter, sugar and vanilla until smooth and creamy. Add the ground almonds and flours and combine until just mixed. It will be crumbly, don't overmix. Gather into a ball, then press it into the bottom and sides of a tart pan or pie pan. Prick crust with fork all over. Chill for an hour in the refigerator, or cover and freeze for up to 2 weeks.
3. Meanwhile, preheat oven to 350 degrees F. Remove crust from refrigerator and cover with foil, then place pie weights or dried beans on top. Bake for 12 minutes. Remove foil and weights/beans. Bake for an additonal 10 minutes or until golden.. Cool completely on a wire rack. Remove outer rim from tart pan before filling, if desired.
Best used as a crust for a filling that doesn't need to be baked. And, if your crust crumbles before you fill it, you can always use the crumbs like I did!